Relating clinical study design to basic research.

Devising any research study involves careful attention to its design, as well as the development of an appropriate research question and hypothesis. Together, these attributes ensure the validity of the study in question. In most clinical or epidemiological studies, the types of research designs are often explicitly noted, whereas in papers describing basic or biological research, they are couched in different terms or, more often, are ignored, thus potentially hindering communication between basic and clinical researchers. However, given that the framework for all valid scientific research is based on sound logic, it is proposed that for each study design, a direct homology exists between clinical and basic research paradigms, despite the problem of relating epidemiological vernacular to basic research. By applying examples of basic research protocols to traditional clinical study designs, this paper shows that parallels can be drawn between the two strategies, suggesting that in the absence of a conventional nomenclature to describe basic research study designs, the use of traditional clinical design jargon is valid in describing basic research protocols.

Spatial repositioning of centromeric domains during regrowth of axons in nuclei of murine dorsal root ganglion neurons in vitro.

Specific chromatin domains within interphase nuclei are organized in cell type specific distributions and are rearranged in association with changes in cell function. Axotomy leads to changes in gene expression. Dorsal root ganglion (DRG) neurons in vitro are a model for axotomy because they are detached from their axons in preparation for the culturing procedure. In a test of the hypothesis that neurons regrowing in vitro undergo rearrangement of specific chromatin domains, changes in the distribution of centromere-associated kinetochores proteins within DRG neurons were assessed as a function of time in vitro. Camparison of the kinetochore distributions in neurons in situ to those 24 h after placement into culture showed that the mean proportion (+/-S.E.M.) of kinetochore signals in the karyoplasm decreased from 41.0 +/- 1.8% to 28.6 +/- 3.3%, while the proportion at the nucleolus increased from 35.2 +/- 2.0% to 48.4 +/- 2.9%. This indicated redistribution of centromeric domains to the nucleolus. Between 1 day and 16 days in vitro, signals were redistributed to the nuclear periphery, indicated by an increase in the proportion of signals in this nuclear compartment from 23.0 +/- 4.3% to 37.6 +/- 3.4% and a decrease in the proportion of signals from 48.4 +/- 2.9% to 23.0 +/- 2.3% at the nucleolus. The results indicate that neurite regrowth following axotomy is associated with changes in nuclear topology. The reorganization that occurs within 24 h is speculated to be associated with a recapitulation of a cytoskeletal development program, while later changes in centromeric distributions may be related to cues elicited by in vitro conditions.

Diethylstilbestrol alters the morphology and calcium levels of growth cones of PC12 cells in vitro.

Diethylstilbestrol (DES) is a synthetic estrogen with carcinogenic properties. DES is known to alter cytoskeletal components, including the organization of actin stress fibres in C6 rat glioma cells. In a test of the hypothesis that DES disrupts actin filaments of growth cones in neuron-like cells, DES-induced changes in filopodial lengths were quantified in rat pheochromocytoma (PC12) cells in vitro. DES significantly altered growth cone morphology, with collapse of growth cone filopodia and neurite retraction invariably occurring at a concentration of 10 microM. At 5 microM DES, transient reductions in total filopodial lengths occurred. At DES concentrations of 0.1 nM and 1 nM, reductions in total filopodial lengths occurred in a fraction of growth cones. Evidence exists which shows that growth cone activity and morphology are intimately linked to levels of intracellular, free calcium and that DES increases such levels. Measurements of free intracellular calcium levels by fluorescence microscopy, at times concurrent with the DES-induced reduction in total filopodial lengths, showed that calcium levels were indeed significantly increased by 10 microM DES. Labelling of filamentous actin (f-actin) with FITC-phalloidin showed that the f-actin distribution in growth cones exposed to DES could not be differentiated from the distribution found in spontaneously retracting growth cones. Together with evidence which showed that growth cone motility was not affected, the results are taken to indicate that DES, rather than acting directly on the cytoskeleton, exerts its effects indirectly, by a calcium-induced destabilization of actin filaments in the growth cone.